A patient presents with sudden severe headache, cocaine use, and left pupil dilation; most likely condition?

• A. Cerebral aneurysm
• B. Migraine
• C. Sinus headache
• D. Tension headache

Answer: (A)

Sudden, severe headache is a hallmark of subarachnoid hemorrhage from a ruptured intracranial aneurysm. Cocaine use raises blood pressure and stresses cerebral vessels, increasing the risk of rupture. The unilateral dilated pupil suggests cranial nerve III involvement, commonly due to a posterior communicating artery aneurysm pressing on the nerve, which can accompany aneurysmal rupture and indicate potential mass effect or early herniation. Together, these signs point to a ruptured cerebral aneurysm with subarachnoid hemorrhage.

Migraine, sinus headache, and tension headache typically do not cause a thunderclap onset with new focal neurological signs like a dilated pupil, so they don’t fit this acute, high-risk presentation. Immediate evaluation with brain imaging and vascular studies is essential in this scenario.